Fully-Integrated SPAD-Based Receiver With Nanosecond Dead Time for Optical Wireless Communication

Abstract

This paper presents the design and characterization of a fully-integrated receiver based on single-photon avalanche diodes (SPADs) with nanosecond dead time for high-speed high-sensitivity optical wireless communication (OWC). The receiver consists of a 4x4 SPAD array that is based on a p-well/deep n-well (DNW) structure, and each SPAD is integrated with a tunable front-end circuit to perform quench and reset. In addition, an OR tree is designed to combine the 16 channels of output from the front-end circuits to generate a single data stream for signal processing, and an output buffer is implemented as the interface to drive 50-Ω loading for testing purpose. Fabricated in a standard 180 nm CMOS process, the receiver achieves a minimum dead time of about 2.5 ns. Bit error rate (BER) measurement of the implemented receiver indicates a sensitivity of -33.9 dBm at 100 Mb/s for a BER of 2x10 -3 and a wavelength of 520 nm, where on-off keying (OOK) modulation and a 2 15 -1 pseudorandom binary sequence (PRBS-15) are employed. To recover the transmitted data stream from the received signal, a signal processing flow specific for SPAD-based receivers is proposed and implemented.

A BiCMOS Active Quencher Using an Inverter-Based Differential Amplifier in the Comparator

“…For a p+/n-well SPAD with an active area of 90 µm² and an excess voltage of 0.5 V the simulated quenching time was 0.1 ns with an AQC in 65 nm CMOS [9]. The simulated quenching time of a p-well/n-well SPAD with an active diameter of 13 µm from an excess bias voltage of 1.8 V was about 0.4 ns in 0.18 µm CMOS [10].…”